This study found that higher overpotential from higher plating current density and a thinner seed layer resulted in more incorporation of sulfur impurities into a deposited copper film. Our results suggested that the higher plating overpotential resulted in smaller copper grains with more grain boundaries where more impurities were trapped. To achieve a defect-free filling in vias, the optimization of the plating current density and the seed layer thickness was necessary. A copper seed with thickness less than 30 generated a sulfur-rich copper film, while, thickness larger than 200 nm for 0.13-nm technologies, the copper seed led to a poor gapfilling with a void after electroplating. (c) 2005 Elsevier B.V. All rights reserved.